Short wavelength laser systems for applications

Author

Sharp, Tracy Elizabeth

Date

1993

Advisor

Young, James F.

Degree

Doctor of Philosophy

Abstract

Very short wavelength lasers have many potential scientific and technological applications. A practical extreme ultraviolet (XUV) laser system has been developed using the Xe Auger laser at 109 nm. This system is the first XUV laser system pumped by a standard, commercially available, Nd:YAG laser system at a high repetition rate. The Xe laser is pumped by the soft x-rays generated by a laser-produced plasma. A grazing incidence, traveling-wave pumping geometry is used to reduce the pump energy required to achieve saturated energy outputs. A total equivalent small signal gain of exp(25) has been achieved with a 20 cm long gain region. The maximum output energy of this system is about 1 $\mu$J.
The extension of the laser-produced plasma pumping technique to extremely short wavelength lasers will require very high power, ultrafast laser pulses in order to produce sufficient upper state densities for gain within the short lifetime of the excited state. To this end, we have studied a new ultrashort laser pulse amplifier based on the broad bandwidth XeF(C $\to$ A) excimer transition that is capable of directly amplifying pulses as short as 10 fs duration and has high energy storage capability. Construction of a tunable, blue-green, subpicosecond source of laser pulses for injection into the XeF(C $\to$ A) excimer amplifier is described. Gain characteristics of the XeF(C $\to$ A) excimer amplifier were investigated for several pulse lengths. Saturation energy densities of 50 mJ/cm$\sp2$ and 80 mJ/cm$\sp2$ were measured for injected laser pulse durations of 250 fs and $\sim$100 ps, respectively. A gain bandwidth of 60 nm was observed. Using an optimized unstable resonator design, the laser amplifier produced 275 mJ pulses with a duration of 250 fs, and a 2.5 times diffraction limited beam quality, making the XeF(C $\to$ A) excimer amplifier the first compact laser system in the visible spectral region to reach peak powers of the terawatt level.